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A. Valente et al.: A compilation of global bio-optical in situ data 
Earth Syst. Sei. Data, 8, 235-252, 2016 
www.earth-syst-sci-data.net/8/235/2016/ 
Figure 8. Global distribution of chlorophyll a concentration per in 
tervals of the observed value. All chlorophyll data were considered, 
but for a given station HPLC data were selected if available. 
Figure 9. Global distribution of chlorophyll a concentration per 
dataset in the final table. All chlorophyll data were considered, but 
for a given station HPLC data were selected if available. 
Indian oceans). Of the contributing datasets, NOMAD and 
SeaBASS provide a good spatial coverage in many regions 
(Fig. 9). The ICES and MERMAID data are mainly located 
along the coastal regions of Europe. The AMT data cover the 
central part of the Atlantic Ocean. For additional analysis and 
as an example of the applications of the compiled dataset, the 
combined chlorophyll data (chla_fluor and chla_hplc) were 
partitioned into 5° x 5° boxes and for each box the number 
of observations, average value and standard deviation were 
computed (Fig. 10 a, b and c, respectively). The number of 
observations can be very high (> 1000) in some boxes along 
the European and North American coastlines and relatively 
low (<20) in oceanic regions. Again there is an appearance 
in the average value map (Fig. 10b) of well-known biogeo- 
graphical features, such has the lower chlorophyll in the sub 
tropical gyres and high values in coastal and upwelling areas. 
There is a close correspondence between the spatial patterns 
of the averaged and standard deviation maps (Fig. 10 b and 
c), which may be an indicator of the data quality. 
Coincident observations of chlorophyll a concentration 
and remote-sensing reflectance are available at 3562 sta 
tions. These observations are mostly from NOMAD (85 %), 
MERMAID (10%) and SeaBASS (5%). The maximum 
of three band ratios of remote-sensing reflectance is 
-180" -120" -60" 0° 60° 120° 180" 
Figure 10. The chlorophyll a (mgm -3 ) data partitioned into 
5° x 5° boxes showing the (a) number of observations, (b) average 
value and (c) standard deviation in each box. All chlorophyll data 
were considered, but for a given station HPLC data were selected if 
available. In the standard deviation plot, grey represents boxes with 
zero standard deviation (i.e. one observation). 
plotted against chlorophyll a concentration (Fig. 11). 
The chla values used are the combined HPLC and flu- 
orometric chlorophyll a, and for rrs the closest spectral 
observation within 2nm was used. The maximum band 
ratios were calculated using the maximum value from 
[rrs(443) / rrs(555), rrs(490) / rrs(555), rrs(510) /rrs(555)] 
or [rrs(443) / rrs(560), rrs(490) / rrs(560), 
rrs(510) / rrs(560)] if rrs(555) was not available. The 
relationship between maximum band ratio and chlorophyll 
is close to the NASA OC4 and OC4E v6 standard algorithm 
(http://oceancolor.gsfc.nasa.gov/cms/atbd/chlor_a), equally 
based on maximum band ratios, providing confidence in the 
quality of the compiled data. 
The inherent optical properties (aph, adg and bbp) are 
available at 27 unique wavelengths between 405 and 683 nm. 
There are a total of 1276, 1123 and 638 observations for 
aph, adg and bbp, respectively. For aph the total num 
ber of observations is distributed among NOMAD (1190),